Producing coked agglomerates



Sept. 13, 1932. E. H. BUNCE 1,877,123

PRoDucING com; AGGLOMERATES Filed July 5o, 1929 INVENTQR EARL H. Ell/VCE.

' ATTORNEYS las `the carbonaceous material Patented Sepe v13, 1932 UNITED' STATES PATENT OFFICE EARL H. BUNCE, OF PALMERTON, PENNSYLVANIA, ASSIGNOR T0 THE NEW JERSEY ZINC COMPANY, 0F NEW YORK,

N. Y., A CORPORATION 0F NEW JERSEY PRODUCING COKED AGGLOMERATIS Application led J'uly 30,

This invention relates to the production of coked` agglomerates of mixed metalllferous `material and carbonaceous material, and has for its object the provision'of certain improvements in the preparation and coking of such agglomerates. While the invention, in its broad aspect, aims to provide certain improvements in the production of coked agglomerates of mixed metalliferous and carbonaceous materials, it moreespeciall contemplates the production of coked agg omerates of mixed zinciferous material and car-` bonaceous material, and will hence be herein described with particular reference to the production of such coked agglomerates.

Coked agglomerates of mixed zinciferous and carbonaceous materials constitute a peculiarly advantageous charge for the smelting or reduction of the zinciferous material, particularly in vertical zinc distillation .retorts In the preparation of such coked agglomerates for vertical retort smelting, the major consideration is the strength of the residue after the zinc has been eliminated-briefly characterized as residue strength. Thus, the coked agglomerates must possess suiiicient strength to `pass progressively through thel vertical retort Without breaking down or4 sanding and to provide a residue of suiiicient strength to prevent disintegration bycrumbling, rupturing or abrading. Hence, it is always necessary to know the residue strength of thecoked agglomerates in order' to determinevvhether ornot the agglomerates can be satisfactorily smelted in a vertical retort. #"ITnthe preparation-of these coked agglomcrates,7 itis customary to first separately crush g. zmc ore) and (e. g. coal) yand together lin a frequently tliey `zin'ciiierous material (e.

thento knead these materials Chilean-mill or edge-runner called ay Chaser) to form a mixture that is? suitable for agglomerating. The necessary intimate Contact of the ore and coal particles for "both reduction and ultimate residue strength is advantageously promoted appropriate graded sizing of the yore and coal as described in the copending patent appli'-` cation of Thomas Routson and myself, Serial N o. 301,709, filed August 23, 1928. If

1929. Serial No. 882,278.

necessary, a conditioning agent or a binder, such as sulfite liquor, tar, pitch, or the like, may be added during the treatment in the edge-runner. The mixture thus prepared in the edge-runner is next agglomerated, usually by briquetting, andthen coked 'at temperatures insuiiicient to cause any substantial loss of zinc.

The purpose of coking the agglomerate is to utilize the coke bond for holding the ore and coal particles together. In eoked a glomerates for vertical retort smelting, it 1s very desirable, if not essential, that the coke bond be a cellular or lattice structure intimately bonded with and enveloping the particles of zinc ore, and of suiiicient strength to prevent both splitting up of the ag lomerates during coking and disintegration during the subsequent smelting or reduction. The active bonding or cokmg constituent of the agglomerate mixture (zinciferous and carbonaceous materials) is the bituminous coal or equivalent cokngagent including in the mixture. The amount of bituminous coal, or equivale-nt coking agent, necessary to give satisfactory residue strength is dependent entirely upon the nature of the coal or e uivalent coking agent used.- It has been ound advantageous to include in the agglomerate mixture, as part or all ofthe bituminous coal required for coking, a certain amount of 'a free-flowing coal as described in the aforementioned patent application. These and economic considerations determine the character of the carbonaceous material of the agglomerate mixture, and usually make it desirable in practice to make up the carbonaceous material of a mixture of coals.

The method used in coking the agglom erates is dependent, to a very large extent at least, upon the amount andnature of the' all bituminous coal. The present invention is concerned primarily with the provision of an' improved method of coking these ore and `aus coal agglomerates and is particularl applicable in those localities Where it is esirable to use the minimum amount of bituminous coal or equivalent coking agent.

The method of coking contemplated by the invention may be characterized as rapid coking, since the aim is to form a shell ofcoke on the agglomerate as promptly as possible. This prompt' formation of a shell of coke on the agglomerate is effected by initially subjecting the agglomerate to a high temperature rapid coking treatment so that a substantial layer of coke forms at the surface of the agglo-merate in a relatively short time interval and While the main inner mass of the agglomerate remains substantially unaltered. The high temperature heat treatment is then continued until the entire agglomerate is coked. Thus, in carrying out the invention, the appropriately prepared agglomerates of mixed metalliferous and carbonaceous materials are subjected to such a rapid initial application of heat as to promptly form a shell of coke on the surface of each agglomerate. After the shell of coke has formed on the surface, the heat enetrates further into the agglomerate an cokin progresses until the Whole agglomerate is co e The rapid initial heating of the agglomerates may be effected in any appropriate manner. The ideal practice involves the initial application to each agglomerate of heat at or slightly above the requisite temperature for coking, and in sufficient quantity to immediately form a shell of coke on the agglomerate. treatment is difficult of realization under practical operating conditions, it should be as closely approximated as possible if the optimum advantages characteristic of the invention are to be attained. Accordingly, in practice, a source of heat at or above the temperature required for coking is applied to the body of agglomerates to be coked so as to heat the surface layer of each agglomerate to the coking temperature as promptly as possible. Thus, it may be said that the starting of the coking operation is at or above the finishing temperature of coking, in contradistinction to those coking practices in which the material to be coked is gradually raised to the requisite coking temperature. Furthermore, in the practice of the invention, this high temperature heat, Which is initially aplied to the agglomerates, must be available 1n suieient quantity to rapidly form the contemplated shell of coke on the agglomerate and to continue and complete the coking of the entire agglomerate.

The agglomerates may be subjected to the coking operation Without preliminary drying or heating. By the customary mode of preparation, the agglomerates contain about 6 to 12% by weight of moisture, and are While such a condition of heat therefore relativel moist. lt is a characteristie feature of t e present invention that these relatively moist agglomerates may be immediately subjected to the highest temperature required for coking. It is advantageous to transfer the agglomerates direct from the agglomerating apparatus, for example a briquetting press, to the coking apparatus, Whereb the moist agglomerates are immediately subjected to` the heating medium at a temperature at or above the iinishing temperature of coking.

The coklng operation is preferably conducted by direct contact o'f a gaseous heatlng medium with the agglomerates. This is desirable since it insures the contemplated rapid as Well as uniform heating of the surface of the agglomerates to the requisite coking temperature, and at the same time permits economic and Vefficient transfer of heat from the heating medium to the agglomerates. The charge of agglomerates should be exposed to the heating medium in the form of a relatively shallow or thin body through which a large volume of the heating gas passes at high velocity.

Any appropriate source of heating gas (lnert to the charge under the conditions of coking) may be used in coking the agglomerates by direct heating. The heating gas must be substantially devoid of oxidizing lnfluences. During' the early or formative stage of coking, oxygen or oxidizing influences deleteriously affect the coking constituent or fraction of the agglomerate, and it 1s particularly important that this stage of the coking operation be conducted in the absence of such oxidizing influences. Oxidizing influences should also be avoided during the later stages of the coking operation, since they tend to consume the coke. The heating gas may be producer gas, lllumlnating gas, oil gas, natural gas, cokeoven gas, Water gas, and similar fuel gases, extraneously heated Where necessar The combustion gases resulting from urning such fuel gas, oil or coal (or similar solid carbonaceous fuel) may be used as the heatlng gas. Such combustion gases may be the exhaust gases from a contiguous thermic operation, when using such combustion gases,

it may be desirable or even necessary to add a small quantity of unburned fuel gas to the combustion gases in order to react with or neutralize any oxidizing gases, such as excess oxygen, therein. Other inert gases, such as nitrogen, superheated steam, and the like, may also be used as the direct heating gas.

The heating gas may as a result of its method of production or previous use be of appropriate temperature for the coking operation. Where the gas is too hot for the contemplated coking operation, it should be appropriately cooled, as for example, by steam, water, or the like. If the heating gas v1,877,191; Y l

is not of a sufficiently elevated temperature course, that the su for the coking operation, it must be approto effect the rapi priately heated. This may be advantageousagglomerates char y accomplished by recuperation, or by re- Any suitable a generation, or by adding thereto an a `profor exposing a shallow or pirate volume of a hotter gas, or by com ustglomerates to the heating m ing some of the gas itself or a combustible charge of agglomerates under constituent added thereto for the purpose. 'may be supported ona statio When the heating gas contains or is itself hearth or p a fuel gas, it is frequently advantageous to ported within combust the as exiting from the charge unclined chambe dergoing coking, and to, utilize the resulting continuously, but prefera heat of combustion for heating the gas-exitpermit progressive move ing side of the charge. This may be accomglomerates thereth vplished by adding oxygen to the gas exiting gravity. The from `the charge and supplying the resulttageously be c ing heat of combustion, preferably by radivertical cokin ation, to the gas-exiting side of the body of pending charge undergoing coking. In this manner 391,82

pply of heat is ad d surface coking o acteristic of the invention. y be employed thin bod of aghus, the going coking nary or moving or may be supa vertically disposed or inntermitten'tly or bly arranged to ment of the agrough by the action of invention may very advan-l arried out in the cross-current in my copparatus ma erforated grate,

r operated i g furnace described patent application, 5V iled September 11, 1929.

uate the a certain compensation is elfected for the Merely by way of illustration, I give the natural drop in temperature of the heatingl following specific example of the practice of gas in passin through the body of charge the invention. The zinciferous material and undergoing co ing.

perature of fi'om 800 to 1000o C. and exiting from the body of agglomerates at a temperature of from 700 to 800 C., but not lower lrrlltues dgisti than 550 C. The drop in temperature of Free ow the heating gas in passing through the agcoal) glomerates may be minimized by the extraneous application of heat to the gas-exiting The mlXllr Confallled 10% side of the body of agglomerates, as for eX- 011 the dry Welgh? ample in the manner hereinbefore described. l l`10 3% 0f SUlPhlt The coking of the agglomerates, under thc {IllXlIlg aS a terrlpol'a preferred conditions herein described, will ltS belleqlal aCtlOIl a take from 30 to 90 minutes, depending upon The brlguetted m the size of the individual agglomerates, the WaS COked 1n the CIOSS-curlen depth or width of the body of charge, and furnace hereinbefore mentio the volume and velocity of the heating gas. gas entering one side of the b The coked agglomerates are preferably under transferred Without substantial loss of heat 900 after coking to the zinc distillation retort. temperature of about 700 Where this practice is not followed and it is quired for the complete coki necessary to store and hence cool the coked about 45 minutes." agglomeraties before smelting, they should be shell of coke on eac cooled, directly upon discharge from the est time possible, i cokinfr operation, under reducing or nonlarge a volume of heating oxidizing conditions, such for example as in through that region wher an atmosphere of non-oxidizing or reducing being formed. After gas or in a mass of carbonaceous material, or formed, the interior of th in receptacles, such as sealed cans, from which by the continued passag of the heating gas through Vhile I prefer, in practicing the invention, going coking. The resulti to coke by direct contact with a gaseous heaterates were subsequently s ing medium, the requisite heat for coking cal retort in accordance-wi may be supplied to theagglomerates in any closed in U. S. patent of other appropriate manner, provided, of N o. 1,712,132 and Satisfact air is excluded.

coal were of the hen, in practicing the present invention, and briquetted i the coking operation is carried out by direct tice described in the aforem contact of the aggloinerates with a gaseous and Bunce app heating medium, the heating gas should be' Using roasted and si of such temperature that the surface of each trates, the agglomerate is rapidly heated. to 800 C. or' ing applic higher. l have obtained very satisfactory -vember 1 results with a heating gas entering the body position of agglomerates undergoing coking at a teinfollows;

n accordan lication Seri ing coal (hi-g-h- I- e-sinous-bx-)died going coking at a tempe C. and exiting from the Per cent by weight moisture based of the ore and coal. From 105 quor was added during y binder and also for s a wetting agent.

without drying, t vertical coking ned, the heating y of briquettes rature of about at a C. The time rena rig operation was To produce the desired h briquettein the shortssary to pass as gas as possible e the coke shell is the coke shell is e briquette is coked of a large volume the charge under- 12; ng coked agglommelted in a vertith the practice dis- Breyer and Bunce orily retained their 1C? agglomerated form without substantial deformation or breaking down throughout the entire reduction period.

It is characteristic of the invention that the agglomerates are heated from room temperature to the effective coking temperature in as s hort a time interval as possible. This initial rapid heating produces a shell of coke which prevents excessive losses from abrasion and is strong enough to withstand the internal forces developed by subsequent drying and coking, which tend to rupture the agglomerates. This shell of coke also enables the ag- Vglomerates to withstand the load of the column of agglomerates above it, without deformation. A temperature of 900O C. at the inlet and 650 C. (but not lower than 550 C.) at the outlet of the body of agglomerates undergoing coking, with direct heating, produces the desired shell of coke. The optimum conditions for uniformly producing the shell of coke throughout the body of agglomerates occur with the lowest temperature drop from the gas inlet to the gas outlet. This condition limits the width, or depth, of the body of agglomerates in that region where the coke shell is being formed. I have found a width of about 16 inches very satisfactory in the aforementioned cross-current vertical coking furnace, but this width may be enlarged with higher temperatures and greater gas volunies, provided that an adequate volume of heating gas can be made to pass through the agglomerates without too great a drop in temperature and pressure.

The following table is a log of a coking operation conducted in accordance with the principles of the invention. The agglomerate mixture was of substantially the same composition as ydescribed in the preceding example, and was briquettedinto four inch loaf briquettes, and the briquettes were charged directly finto the coking furnace. This furnace consisted of a chamber containing horizontally disposed grate bars and a flue for conducting the heating gas to the chamber below the grate bars. The briquettes were placed on the grate bars and the heating gas from the fluepassed upwardly throughthebed of briquettes and was exhausted to the atmosphere. The heating gas was delivered to the briquettes at a temperature of 900 C. The coking operation was completed in 30 minutes.

Log of colcimg operation Sam- 1:11a;

ple an Appearance ol briquette when removed and numhars broken in half ber c 1 5 M" coke shell-center wet. 2 10 W' coke shell-center wet. 3 l5 V3" coke shell-center plastic. l' y 4 20 Entire brquette solid, but volatile being removed. 5 25 Entire briquette solid, but volatile being removed. 6 30 Entire briquette solid; all volatile removed within a few minutes after charging a substantial layer of coke forms at the surface of the agglomerate while the core is still in its original moist condition. This layer of coke progressively moves towards the center until ultimately the entire agglomerate is coked.` Complete coking of the agglomerate is accomplished in a relatively short interval of time with little or no danger of disrupting the agglomeratie during the coking operation. At the end ofthe coking period, the agglomerate is a homogeneous piece of coke with no indication of layers or zones having been formed. The coke is free from breeze and is dense and strong.

The coking method of the invention is particularly adapted for the economic production of coke and residue strengths. While the invention is of particular advantage for coking agglomerates in which the carbonaceous material consists of a mixture of a free.

flowing coal and anthracite or coke fines, it may be practiced with advantage where the carbonaceous material consists of a blend of bituminous coals including some free-flowing coal, and where the carbonaceous material is a bituminous coal possessing of itself such properties as adapt it for this method of coking. While it is our preferred practice to effect the contemplated coking vaction by bituminous coal, other equivalent carbonaceous coking agents may be substituted in whole or in part for the bituminous coal, suchI as tar, pitch, and the like. Anthracite or coke fines are included in the agglomerate mixture primarily for the purpose of imparting adequate residue strength, and where the use of these fines is uneconomical, other materials not affected by the prevailing conditions of reduction, such as slate coal, sand, saggers, etc., may be substituted in whole or in part for such fines.

'asI

In the foregoing discussion I have particularly described the invention in connection with the production of coked agglomerates of mixed zinciferous and carbonaceous materials. Such coked agglomerates, while peculiarly adapted for smelting in vertical retorts, may be treated by any other appropriate metallurgical operation. Moreover, the invention is not restrict-ed to z/inciferous materials, but may be practiced with advantage in producing coked agglomerates of any other metalliferous material.

The novel features of the inventionwill be best understood from the following description taken in conjunction with the accompanying drawings, in which Fig. 1 is a sectional elevation of acoking furnace adapted forl a practice of the invention; and

Fig. 2 is a cross section of the furnace of Fig. 1 on the section line 2-2. Y

Referring to Figs. 1 and 2 of the drawing,

It is characteristic of the invention that the furnace comprlses a brickwork structure .stantially vertical,

5, of oval horizontal section, having a gas inlet iue 6 and a gas outlet flue 7. Clean-out openings are provided in the curved ends of the structure. A relatively narrow coking chamber 8 is built midway between the ends of the structure 5, thereby providing on one side a gas distributing laboratory or chamber 9 communicating with the inlet 6 and on the other side a similar laboratory or chamber 10 communicating with the outlet 7. One side wall 12 of the coking chamber is subwhile the other side wall 13 is slightly' inclined outwardly so that the cross sectional area of the chamber increases from the top to the bottom. Both side walls of the coking chamber are permeable to the passage therethrough of gas in considerable volume. This permeability `is preferably provided by uniformly distributed openings or slots in each side wall.

In the coking chamber illustrated in Figs. 1 and 2 of the drawing, the vertical side wall 12 is built up of superposed tiles or plates having uniformly distributed slots. These tiles may be made of refractory material, such as silicon carbide alone or. mixed with clay, or of temperature resistant metal alloys, such as alloys of iron, chromium and nickel. The inclined wall 13 is built of louvers positioned so that the gas stream leaving the coking chamber is directed upwardly into the gasexiting chamber 10. This louver construction minimizes the possibility of dust and broken pieces of agglomerates lodging in and choking the openings on the gas-exit side of the colungchamber.

The upper end of the coking chamber passing through the roof of the furnace structure 5 has a water jacket 21. A charging extension or hopper 22 provided with a swinging gate 23 is mounted above the water jacket. A pipe 24 connects the extension 22 with the gasexit-ing chamber 10, which is adapted to remove by suction oxidizing air entrapped in the charge hopper 22 and also to remove by suction any heating gases that may rise upwardly through the column of agglomerated charge materials into the hopper 22.

A discharging device consisting of an in clined chute 25 and a rotatably mounted cylinder 26 is operatively associated with the lower end of the coking chamber 8. The lower end of the chute is closed by a pivotally mounted gate 27 biased to its closed position by a counterweight 28. A pipe 29 connects the lower end of the chute with the gas-exiting chamber 10.

When the furnace is in operation, the coking chamber 8 is filled with agglomerates undergoing coking. Periodically, an appropriate amount of coked agglomerates is withdrawn from the chamber by opening the gate 27 and rotating the cylinder 26, and simultaneously a corresponding amount of fresh agglomerates is introduced into the hopper 22. The

,'lfhus, the heating gas contemplated coking coking chamber is thereby maintained full and the green or fresh agglomeraties are charged with a minimum drop or fall. v

The heating gas for coking is introduced through the gas inlet 6. Any appropriate source of heating gas (inert to the charge under the conditions of coking) may be used. may be producer gas, illuminating gas, oil gas, natural gas, ycoke oven gas, water gas, and similar fuel gases, extraneously heated when necessary. The combustion gases resulting from burning such fuel gases, oil or coal (or similar solid carbonaceous fuel) may be used as the heating gas. Such combustion gases may be the exhaust gases from a contiguous thermic operation. When using such combustion gases, it may be desirable or even necessary to add a small quanti-ty of unburnt fuel gas to the combustion gases in order to react with or neutralize any oxidizing gases, such as excess oxygen therein. Other inert gases, such as nitrogen, superheated steam, and the like, may also be used as 'the heating gas.

The heating gas must be substantially de-` void of oxldizing influences. During the early or formative stage of coking, oxygen or oxidizing influences deleteriously aiiect the coking constituent or fraction of the agglomerate, and it is particularly important that this stage of the coking operation be conducted iluences. Oxidizing influences should also be avoided during the later stages of the coking oplration since they tend to consume theco e.

The heating gas may as a result of its method of production or previous use be of appropriate temperature for the coking operation. Where the gas is too hot for the operation, it should be appropriately cooled as, for example, by steam, water or the like. If the heating gas is not of a sui'liciently elevated temperature for the coking operation, it must be appropriately heated. This may be advantageously accomplished by recuperation, or by regeneration, or by adding thereto an appropriate volume of a hotter gas, or by combusting some of the gas itself or a combustible constituent added thereto for the purpose. f

The heating gas enters the chamber 9 and is distributed through the openings of the vertical wall 12 into the coking chamber 8. The gas flows transversely through the body of agglomerates in the coking chamber and out through the openings in the sloping side wall 13 into the chamber 10, and to the gas outlet 7. The heating gas may be forced vthrough the furnace, but is preferably drawn in the absence of such oxidizing iny through by suction fans communicating with Aso provision of the pipe 24 which serves to suck the air from the hopper into the gas-exiting chamber 10. Even When the sWin ing gate 23 is closed, some air is likely to lea into the charging hopper, and such air is likewise drawn through the pipe 24 into the chamber 10. Similarly, the pipe 29 draws any air entering the discharge chute 25 into the chamber 10. The draft created by the exiting gases in the flue 7 establishes a sulicient suction in the pipes 24 and 29 to inhibit the floyv into the active coking zone of the chamber 8 of any' oxidizing gas resulting from the entrance of air through either the charging or discharging device. Where the heating gas is forced through the furnace (instead of drawn through by suction as in my preferred practice), the pipes 24 and 29 are omitted, since they Would be inoperative in that case.

I claim:

1. The method of producing coked agglomerates which comprises preparing and agglomerating a mixture of metalli erous material and an appropriate coking agent, subjecting the agglomerates to a coking operation n which the agglomerates are initially heated by direct contact with a aseous heating medium (passed therethrough in Sullicient volume an at a suiicientl highy temperature to promptly form a she l of coke on each agglomerate, and continuing the heating of the a glomerates until coking thereof is complete 2. The method of producing coked agglomerates which comprises reparing and agglomerating a mixture ofp metalliferous material and carbonaceous material, subjecting the agglomerates to a coking operation in which the agglomerates are initially heated b direct contact with a gaseous heating medium introduced into the agglomerates at a temperature at least as high as the eective coking temperature and leaving the agglomerates at a temperature not less than 550 C. and thereby promptly forming a shell of coke on each agglomerate, and continuing the heating of the agglomerates until coking thereof is completed.

3. The method of producing coked agglomerates which comprises preparing an agglomerating a mixture of metalli erous material and carbonaceous material, subjecting the agglomerates with a substantial moisture content to a coking operation in which the agglomerates are initially heated by direct contact with a gaseous heating medium passed therethrough in suiiicient volume and at a sufficiently high temperature to promptly form a shell of coke on each agglomerate, and continuin the heating of the agglomerates until co ing thereof is completed.

4. The method of producing coked agglomerates which comprises preparing and agglomerating an intimate mixture of zincoperation in iferous material and carbonaceous material,

subjecting the ag lomerates to a coking operation in which t e agglomerates are initially heated b direct contact with a aseous heating me ium assed therethrou h in sufficient volume and) at a sulliciently igh temperature to promptly form a shell of coke on each agglomerate, and continuing the heating of t e agglomerates until coking thereof is completed.

5. The method of producing coked agglomerates which comprises preparin and agglomerating an intimate mixture o zinciferous material and carbonaceous material, subjecting the agglomerates to a coking operation in which the agglomerates are initially heated by'direct contact with a gaseous heating medium introduced into the agglomerates at a temperature at least as high as the effective coking temperature and leaving the agglomerates at a temperature not less than 550 C. and thereby promptly forming a shell of coke on each agglomerate, and continuing the heating of the agglomerates until coking thereof is completed.

6. The method of producing coked agglomerates which comprises preparing and agglomerating an intimate mixture of zinciferpus material and carbonaceous material, subjecting the aggl nerates with a substantial moisture content to a coking operation in which the agglomerates are initally heated by direct contact With a gaseous heating medium passed therethrou h in sufficient volume and atasuiciently hig temperature to romptly form a shell of coke on each agg omerate, and continuing the heatin of the agglomerates until coking thereo is completed.

7. The method of producing coked agglomerates? Which comprises preparing and agglomerating an intimate mixture of zinciferous material and carbonaceous material, subjecting said agglomerates to a coking which the agglomerates are initially heated by direct contact with a gaseous heating medium passed therethrouglh in suficient volume and at a sufficiently igh temperature to promptly form a shell of coke on each agglomerate, and continuin the heating of the agglomerates until coking thereof is completed and thereby producing coked agglomerates possessing adequate residue strength when subjected to vertical retort smelting.

8. The method of producing coked agglomerates which comprises preparing and agglomerating an intimate mixture of zinciferous material and carbonaceous material, subjecting said agglomerates to a coking operation inwhich the agglomerates are initially heated by direct contact with a gaseous heating medium introduced into the agglomerates at a temperature not lower than 800 C. and leaving the agglomerates at a temperature not less than 550 C. and thereby promptly forming a shell of coke on eachagglomerate, andsmelting, subjecting said agglomerates with a moisture content of about 6 to 12% on the dry weight thereof to a coking operation characterized by an initial application of heat to the agglomerates at a temperature at or above the requisite coking temperature and thereby promptly forming a shell of coke on each agglomerate, and continuing the application of heat to the agglomerates until the entire mass of each agglomerate is heated to the requisite coking temperature.

10. The method of producing coked` ag- A glomerates which comprises preparing and j agglomerates, until coking thereof 1s com-` agglomerating anintimate mixture of zinciferous material and carbonaceous material capable when appropriately coked of producing coked agglomerates possessing satis.

factory residue strengthfor vertical retort smelting, subjecting said agglomerates with a moisture content of about 6 to 12% on the dry Weight thereof to a colng operation in which-the agglomerates vare initially heated by direct contact with a gaseous heating medium passed therethrou h in sufficient volume and at a sufficiently igh temperature t0 promptly form a shell of coke on each agglomerate, and continuing the heating o f the agglcmerates until coking thereof 1s complete 11. The method of producing coked agglomerates which comprises preparing and afgglomerating an' intimate mlxture of zinci erous material and carbonaceous material capable when" appropriately coked of prolucing coked agglomerates possessing satisfactory residue strength for. vertical retort smelting, subjecting said agglomerates with a substantial moisture content to a coking operation in which the agglomerates are initially heated by direct contact with a gaseous heating medium passed therethrou h in suicient volume and at a suiiciently hig temperature to promptlyform a shell of coke on each agglomerate, and continuing the heating of the pleted.

12. In the method of coking agglomerates containing an inti te admixture of zinciferous and carbon?a including a coking agent, the steps which comprise subjecting an upper section of moving continuous column of the agglomerates to intensiveheat treatment adapted to form a shell of coke on each agglomerate in said upper section of the column in a short time interval to fix the shap crates before they are sof by overhead agglomerate the heat treatment operati coked agglomerates as th ly lowered in the column lerates until their interior In testimony whereof I aiix my signature.

EARL H. BUN CE.

e of the agglomtened and crushed s, and continuing on of the partially ey are progressiveof moving aggloms are coked.

ceousreducing materials lors 

